1. Field of the Invention
The present invention relates to a powder containing Fe—Ni nano-particles and its manufacturing method, and particularly to a powder having a film of Fe—Ni nano-particles deposited on the surface. The powder containing Fe—Ni nano-particles has very small volume and very large surface area. The contact chance between Fe/Ni bimetal and chlorinated organic substance is largely increased. It can be used to treat various environmental pollutants or for some catalytic reactions, and particularly to treat the organic pollutants containing chlorine in environment.
2. Description of the Prior Art
The chlorinated organic substance generally has strong toxicity, which are rather dangerous to the human body and the environment of living things. For example, tetrachloroethene (PCE) and carbon tetrachloride (CT) have been proved to be able to cause cancer on human body, and the other various chlorinated organic substance are also possible for human to cause cancer. The chlorinated organic substance such as chloroform (CF), trichloroethene (TCE), dichloromethane (DCM), PCE and CT etc. are widely used in industry. They are chiefly used for degreasing, dyeing, cleaning and printed circuit manufacturing processes. These kinds of compounds are rather stable and not easy to be resolved. Their resolvability in water is low and easy to accumulate in soil and underground water so that they after become the general pollutants in soil and underground water. Therefore, besides to make law to prevent the chlorinated organic substance from entering the environment, the place that has been polluted by the chlorinated organic substance must be treated and remedied as quickly as possible.
The chlorine atom has high electronegativity and can adsorb electrons from neighborhood, so the most carbons in the chlorinated organic substance exist at relatively high oxidation state and the chlorine in the chlorinated organic substance can be resolved and removed by the reduction method. Because the iron metal has rather high reducing power, i.e. able to provide electrons, it can be used to resolve various chlorinated organic substance such as chlorinated methane, chlorinated ethane, trichloroethene, tetrachloroethene, trichloroethane, and trichloromethane etc.
Although the iron metal can effectively resolve the chlorinated organic substance, it would occur that the pH value does increase in the dechlorine process and the surface of the iron particle does form some iron oxide in the environment containing water and is covered up, so the activity of the iron is reduced and the ability for resolving the chlorinated organic substance is lowered.
In order to improve the drawback of the iron metal as stated above, the second kind of metal such as Pd, Ni, Ag, Cu, and Au is added in the iron to form bimetal, keep the dechlorine activity for iron surface and promote the reaction of dechlorine. Among these metals, Ni has catalysis and anti-corrosion in water, so it is relatively often used to form Fe/Ni bimetal for dechlorine.
The ability of bimetal, for removing the chlorinated organic substance, is higher than iron metal. For resolving the chlorinated organic substance, the dechlorine substance needs possess both the reducing power and large surface area. The more the surface area, the higher the dechlorine power. Therefore, it is necessary that the bimetal is made into micro-particles with large surface area. The micro-particle of metal as a dechlorine agent cannot only promote the surface contact and reaction but also increase the penetrative power in the contaminated soil to promote the treatment effect.
The volume of the metal particle must be decreased to increase its surface area. If the volume of the metal particle is too small, it will quickly penetrate through the soil and easily flows away. Therefore, the time of contact and reaction between metal and chlorinated organic substance becomes too short and the effect of removing chlorinated organic substance by metal is lowered. The problem of penetration and loss of the metal particle must also be considered when the volume of the metal particle is reduced to increase the surface area.
In addition, it is rather difficult in technique how to make micro-particles of Fe—Ni bimetal, especially particles with nanometer size. In the prior technique, the nano-particles of iron metal are first made, and subsequently the iron nano-particles are put into the solution containing Ni++ to make the Fe atoms on the surface of the particles be replaced by the Ni atoms. The reducing reaction is shown in the following:Ni+++Feo→Fe+++Nio 
But the Fe—Ni particles made by this way are strictly not the real Fe/Ni bimetal, they are only the iron particles of which surface are covered with a film of Ni. Only the film of Ni can touch the chlorinated organic substance to proceed the reducing and resolving reaction, and the Fe atoms inside have no chance to touch the chlorinated organic substance at all.
In order to get the real Fe—Ni nano-particles, of which Fe and Ni atoms can simultaneously exist on the surface of the particles and have the same chance to touch with chlorinated organic substance and proceed reducing and catalyzing reaction, and to prevent the particles in the contaminated soil from flowing away due to their small volume. Therefore, the present invention provides a powder and its manufacturing method, which can solve the all problems as stated above.